In a conventional battery two solid electrodes are immersed in a fluid-like substance that allows for flow of chemicals - when charged, the battery chemistry enables the liquid to huddle up to the solid electrodes so electrons flow out of the battery and into the circuitry you're using. To charge it up, you push electrons back in to the battery, and the internal chemistry re-arranges itself ready to be discharged.
MIT's system uses a semi-solid flow cell, whereby the electrodes and battery fluid (electrolyte) are still separate, but they're all mingled up as a sludgy liquid. The electrodes are made of tiny particles suspended in liquid electrolyte, and to discharge it you pump the fluid through a filter, allowing electrons to flow out of your battery.
MIT's energy dense 'Cambridge Crude' allows for less bulky designs than is usually possible, meaning EV components - battery, electronics, and motors - could be more easily dropped into conventional car designs. It also allows for battery swapping and for sludge exchange, whereby "spent" fuel is pumped out and replaced with new fully charged battery chemistry. That spent fuel could be charged up at the station, and then injected into the next nearly empty battery that drove up.
Moments to charge your EV instead of hours? Fingers crossed.
